We are studying transport of organic nutrients (sugars, amino acids, constituents of nucleic acids) in ocular tissues. To date, work has been done primarily on the lens (bovine, rodent). The systems of transport are analyzed in vitro for saturability, dependence on alkali metal cations, and specificity. Efforts will also be made to determine whether the substrates are accumulated by incubating non-metabolizable compounds for various periods of time. The effect of differentiation of the epithelial cells of the bovine lens to fiber cells on systems of transport can be examined conveniently by incubating on vials on stirred medium with either the anterior (epithelia) or posterior (fiber cell) surface in contact with the solution. We intend to expand these studies to the corneal endothelium and the retina.